JPS60236112A - Composite vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain high recording density and to enable ultra-high density recording and reproducing by controlling the apparent coercive force in the direction perpendicular to the plane of a composite medium in a prescribed range. CONSTITUTION:The two-layered medium forms a high permeability layer having 0.7mum thickness on a glass substrate and forms a vertical magnetized film having 0.2mum thickness thereon. The satd. magnetization of the vertical magnetized film is 300emu/cc and the coercive force is changed by changing sputtering conditions. The large density is obtd. where the apparent coervice force of the composite two-layered medium is in a 400-1,200e, more perferably 55-850e range as shown in the figure when the recordable density is measured by changing the coercive force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a recording medium for perpendicular magnetic recording, and in particular to a medium that has excellent recording density characteristics, a large output, and is suitable for high-density recording and reproduction.

[Background of the invention]

(1) Perpendicular magnetic recording media are single-layer media in which a perpendicular magnetic layer is formed on a non-magnetic substrate (the perpendicular magnetic layer is the only layer that actually acts magnetically during recording and reproduction), and a perpendicular magnetic layer with high permeability. There is a so-called two-layer film medium formed on a magnetic layer. Although dual-layer media are considered suitable for ultra-high density recording and reproduction,
Until now, no optimal design has been made, and recording and reproduction of dual-layer film media is not necessarily better than that of single-layer film media.

[Purpose of the invention]

An object of the present invention is to provide a two-layer film medium that has superior recording and reproducing characteristics compared to a single-layer film medium.

[Summary of the invention]

We fabricated various composite perpendicular magnetic recording media by changing the magnetic properties of the high permeability magnetic layer and the perpendicular magnetic layer, and evaluated the recording and reproducing characteristics.As a result, we found that the apparent coercive force of the composite media could be reduced to a very narrow range. It was found that excellent properties could not be obtained unless controlled.

[Embodiments of the invention]

FIG. 1 shows the relationship between the apparent perpendicular coercive force HC1 of a two-layer medium and (2) recordable/reproducible density DI58. The coercive force was measured by applying a magnetic field perpendicular to the surface of the medium, sufficiently magnetically saturating the medium with a magnetic field of about 10 KOe or more, and using a vibrating sample magnetometer.

The two-layer medium is a glass substrate, on which a Co-Mo-Zr high magnetic permeability layer is formed to a thickness of 0.7 μm by RF sputtering, and on top of this a Co-Cr perpendicular magnetization film is formed to a thickness of 0.2 μm by RF sputtering. The high magnetic permeability layer formed by the method had a saturation magnetic flux density of about 7 kG and a magnetic permeability of about 800. The saturation magnetization of the perpendicularly magnetized film was about 300 amu/cc, and the coercive force was changed by changing the sputtering conditions.

The recording and reproducing characteristics use a ferrite ring head with a magnetic gap length of 0.2 μm, and a relative speed of 2.5 m/s1? It was measured.

The recording density D6o was defined as the recording density at which the output at low recording density decreased to 50%.

As shown in Figure 1, the apparent coercive force H of the composite two-layer medium
cm is 4O-1200e, preferably 50-1000e
, more preferably in the range of 55 to 85o8, a particularly large angle of 50 is obtained, (3) It can be seen that the present invention is excellent.

For comparison, we also investigated the recording and reproducing characteristics of a single-layer film medium in which a Co-Cr perpendicular magnetization film was directly formed on a glass substrate without forming a Co-Mo-Zr high magnetic permeability layer.
Only a low value of I was obtained compared to the two-layer film medium of the present invention.

In this example, c was used as the base high magnetic permeability layer.

-Although the case of Mo-Zr amorphous alloy has been described, Ni-F
It may be formed of a general high magnetic permeability material such as e-alloy, and the magnetic permeability may be 200, preferably about 800 or more, and the thickness may be within a range where magnetic saturation does not occur significantly during recording. Further, the recording medium is not limited to Co--Cr alloy, and it goes without saying that a general perpendicular magnetization film may be used.

〔Effect of the invention〕

According to the present invention, since a high recording density can be obtained, ultra-high density recording and reproduction becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a curve diagram for explaining the present invention in detail. (4)

Claims (1)

[Claims] 1. In a composite perpendicular magnetization medium in which a perpendicular magnetization layer is formed on a high permeability magnetic layer, the apparent coercive force H8↓ in the direction perpendicular to the surface of the composite medium is in the range of 40 to 1200e. A composite perpendicular magnetic recording medium characterized by: 2. The composite perpendicular magnetic recording medium according to claim 1, having an apparent coercive force within the range of 50 to 1000e. 3. The composite perpendicular magnetic recording medium according to claim 1, having an apparent coercive force within the range of 55 to 850e.